The present invention relates to a heat exchanger and manufacturing method thereof and, more particularly, to a split heat exchanger having oval tubes for a cooling cycle and a manufacturing method thereof and in which several fin groups are arranged in layers with the tubes forming pipe rows having a zigzag pattern.
Heat exchangers are generally used in air conditions, refrigerators, etc. to carry out heat exchange between external air passing over fins and the external surface of pipes thereof through which refrigerant flows. Generally, there are split-fin type heat exchangers in which a plurality of fins are arranged depth-wise in parallel with each other and additionally in groups and the fin groups are piled longitudinally in layers, and integral-fin type heat exchangers in which a plurality of fins are arranged depth-wise in parallel with each other in one layer.
A conventional split-fin type heat exchanger 1, as shown in FIG. 1, comprises a plurality of plate-shaped fins 3 disposed depth-wise in parallel with each other and refrigerant pipes 2 passing through the fins 3 numerous times by being bent in a U-shape.
As shown in FIG. 2, the fins 3 are arranged in layers along the longitudinal direction of air flow (shown by the arrow F in the drawing). A couple (two) of through-holes 3a, through which the pipes 2 are inserted, are provided by perforation on the respective fins 3. Each pipe 2 is hollow and cylindrical, and passes through the fins 3 from the longitudinally uppermost fin group to the lowermost fin group by being bent depth-wise in a series of U-shapes. In the heat exchanger, there are two longitudinal pipe rows of the two pipes 2 which are held separated from each other in a lateral direction by the fins 3. Each pipe row of a pipe 2 is arranged in a single plane along the longitudinal direction of air flow. Reference numeral 4 is a defrosting heater.
In order to assemble such a conventional split-fin type heat exchanger 1, a plurality of fins 3 in which a couple of through-holes 3a have been perforated are arranged depth-wise in parallel with each other, and then a couple of pipes 2 penetrate the fins 3 depth-wise through the respective through-holes 3a. At this stage, the fins 3 are arranged depth-wise in several groups, the fin groups having inner pipe portions therein and being separated depth-wise from each other at predetermined intervals by outer pipe portions. Then, the pipe outer portions which are located between the fin groups are bent depth-wise in a U-shape so that the fin groups are piled in layers in a longitudinal direction of the heat exchanger 1. After this, the openings of the two pipes 2 at the lower longitudinal end are welded so as to connect the pipes 2 into a single flow path.
However, in the above prior art heat exchanger 1, as shown in FIG. 2, since each pipe row is arranged in a single plane along the longitudinal direction of air flow, external air which flows longitudinally between and outside of the pipe rows of the pipes 2 passes through the heat exchanger 1 without effectively contacting the pipe portions of pipes 2. In addition, after external air which is forwarded toward the bottom of the heat exchanger 1 contacts the lowermost pipe portions, the air is mostly dispersed or channeled as shown by the flow arrows and bypasses the above pipe portions which are adjacent to the lowermost pipe portions. As a result, heat exchange efficiency is greatly decreased.
Further, because the pipe 2 is formed in a cylindrical shape, the amount of space provided for the passage of air is limited such that air directed toward the heat exchanger 1 by a fan (not shown) in the longitudinal direction of the arrows in FIG. 2 loses much of its force by pressure loss, and consumption power and operating noise of the fan are increased. Also, condensed water generated during the defrosting process tends to be suspended on a bottom surface of the pipes 2 and thus the pipe may be frosted immediately after the cooling cycle begins to operate again.
The present invention has been made in an effort to solve the above problems.
It is an objective of the present invention to provide a heat exchanger named SOFT (Split, Oval, Fin and Tube) evaporator and manufacturing method thereof in which arrangement of a pipe is improved to enhance heat exchange efficiency by increasing air contact area with the pipe.
It is another objective of the present invention to provide a heat exchanger named SOFT (Split, Oval, Fin and Tube) evaporator and manufacturing method thereof in which the shape of a pipe is improved to reduce the pressure loss of air flowing into a heat exchanger and to make condensed water exhausted more easily therefrom.
To achieve the above objectives, the present invention provides a heat exchanger, for example for a cooling cycle, comprising a plurality of fins which are arranged depth-wise in parallel with each other and pipes which pass through the fins. The fins are arranged depth-wise in groups and the fin groups are piled in layers along the longitudinal direction of air flow. The pipes pass through the fin groups by being bent numerous times at bent portions thereof and the inner portions of the pipes in the fin groups form at least two rows along the longitudinal direction of air flow. The inner pipe portions of each pipe row are arranged in a zigzag shape, pattern or progression.
The pipe is preferably oval or elliptically-shaped in cross section to have a short axis and a long axis, and the pipe passes through the fin groups in such a manner that the long axis of the pipe is parallel to the longitudinal direction of air flow.
Preferably, the ratio of a length of the long axis of the pipe to a length of the short axis is in the range of 1.3-1.7.
More preferably, auxiliary plates, having fixing holes through which the bending portion of the pipes are inserted, are fixedly mounted to the front and rear of the layered fin groups.
According to another aspect of the present invention, a method for manufacturing a heat exchanger, for example for a cooling cycle, comprises the steps of: preparing the pipes and the fins having through-holes through which the pipes are inserted; arranging the fins depth-wise in several separated groups and inserting the pipes through the through-holes of the fin groups; bending the outer pipe portions of the pipes located between the fin groups so that the fin groups separated from each other are piled in layers along the longitudinal direction of air flow and so that the inner pipe portions of the pipes in the fin groups are arranged in at least two rows along the longitudinal direction of air flow; and wrenching the bent portions of the pipes to form each pipe row into a zigzag shape.
The preparing step further comprises the step of forming the pipe in an oval or elliptical shape which has a short axis and a long axis, and the fin arranging step further comprises the step of inserting the pipe into the fin groups with the long axis of the pipe parallel to the longitudinal direction of air flow.
In addition, the preparing step further comprises the step of forming the through-holes on a portion biased in a lateral direction from a longitudinal center of the fin, and the fin arranging step further comprises the step of alternately arranging the fin groups to have the through-holes formed on a laterally left-biased portion thereof and the fin groups formed on a laterally right-biased portion thereof.
The method for manufacturing a heat exchanger further comprises the steps of forming a burr on the surrounding portion of each through-hole to provide a surface contact thereof with the outer circumferential surface of the pipe subsequently inserted therethrough; expanding each pipe so that the outer circumferential surface of the pipe adheres closely to the inner circumferential surface of the associated through-hole between the fin arranging step and the pipe bending step; and fixedly mounting respective auxiliary plates, having fixing holes through which the bending portion of the pipes are inserted, to the front and rear of the heat exchanger after the wrenching step.